A lithium-ion secondary battery has characteristics of having a higher energy density and being operable at a higher voltage than other secondary batteries. Therefore, it is used as a secondary battery, which can be easily reduced in size and weight, for information equipment such as cellular phones. In recent years, there is an increasing demand for use of the lithium-ion secondary battery as a large-size power source for hybrid vehicles or the like.
The lithium-ion secondary battery includes a positive electrode layer, a negative electrode layer, and an electrolyte disposed therebetween. The electrolyte includes a nonaqueous liquid or a solid. When the nonaqueous liquid (hereinafter referred to as an “electrolytic solution”) is used for the electrolyte, the electrolytic solution penetrates the inside of the positive electrode layer. Thus, an interface between a positive electrode active material forming the positive electrode layer and the electrolyte is easily formed, resulting in improvement of the performance. However, since a widely-used electrolytic solution is combustible, it is necessary to have a system for ensuring safety. On the other hand, since a solid electrolyte is noncombustible, the system may be simplified. Consequently, there is suggested a lithium-ion secondary battery including a noncombustible solid electrolyte (hereinafter sometimes referred to as a “solid electrolyte layer”).
In the case of a lithium-ion secondary battery having a solid electrolyte layer arranged between a positive electrode layer and a negative electrode layer (hereinafter sometimes referred to as an “all-solid-state battery”), interfaces between the electrolyte and the positive electrode active material and the negative electrode active material are interfaces between solids (solid/solid interfaces). The ion conductive resistance at the solid/solid interface increases easily as compared with that at a solid/liquid interface. Thus, in the case of the all-solid-state battery, it is necessary to reduce the ion conductive resistance at the solid/solid interface (hereinafter referred to as “interface resistance”) by applying pressure to the solid/solid interface.
As a technique related to such an all-solid-state battery, for example, an all-solid-state battery including a wound electrode body formed by winding belt-like positive and negative electrodes through a solid electrolyte and a separator is disclosed in Patent Literature 1.